Conventionally, an optical sorting machine is known for sorting out raw material composed of grains such as rice, barley, wheat, oats, beans and nuts, plastic pieces such as pellets and beads, fine articles such as drugs, ores and volcanic soil, or other granular articles into good articles or defective articles and/or excluding foreign objects and the like contaminating the raw material.
Optical sorting machines of this kind include one of the type in which a chute with a predetermined width is inclined and disposed on the downside of a granular article feeding part.
The optical sorting machine sorts out the granular articles by: feeding a large amount of granular articles to the chute having the predetermined width from the granular article feeding part; irradiating, with light, the granular articles which flow down the chute surface, spreading in the width direction, and which undergo free fall along a predetermined path from the lower end of the chute; receiving the reflected light and the like from the granular articles to detect defective articles, foreign objects and the like contained in the raw material; and excluding the detected defective articles, foreign objects and the like from the predetermined path.
Incidentally, in the above-mentioned optical sorting machine, when the raw material is granular articles with long and thin shapes such as long grain rice, granular articles with viscosity on the surfaces such as parboiled rice, or the like, the plural granular articles overlapping with and/or being joined to one another are liable to cause unevenness of the flow of the granular articles on the chute surface. As a result, there has been a problem that failure in detection of defective articles and the like, and/or failure in exclusion, for example, exclusion of good articles mixed up with the defective articles can arise.
Therefore, as for the optical sorting machines, a chute for preventing unevenness of the flow of granular articles is proposed (see Patent Literature 1).
FIG. 7 shows a schematic diagram for explaining the chute disclosed in Patent Literature 1, FIG. 8 shows a lateral view of the chute shown in FIG. 7. Moreover, FIG. 9 shows an enlarged view of the B part in FIG. 8.
A chute 6 disclosed in Patent Literature 1 includes components 61 to 64 composed of a plurality of plate shapes with flat surfaces.
In the chute 6, the downstream side end part of the component that positions on the upstream side is overlapped with the upstream side end part of the component that positions on the downstream side sequentially, and thereby, the flat surfaces of the plurality of components 61 to 64 are assembled with the steps included to form the surface which granular articles flow down.
According to the above-mentioned chute 6, since the granular articles disperse due to the impacts in dropping over the steps, unevenness of the flow of the granular articles on the chute surface can be prevented.
However, in the above-mentioned chute 6, as shown in FIG. 9, since the granular articles dropping over the step are liable to cause hops thereof, a problem arises that the flow of the granular articles is hardly stabilized on the surface of the component that positions on the downstream side.
Moreover, in the above-mentioned chute 6, since powdery dusts are liable to swirl when the granular articles are dropping over the steps and there is a risk that powdery dusts 65 sticking and deposited on the step part contaminate the granular articles as foreign objects, the step part is needed to be cleaned periodically.